Scroll PLMs are used in the original game to change the scrolling configuration of a room's screens when Samus touches them. This is achieved by running ASM at the location $8F:XXYY, where XX is the High byte, and YY is the Low byte.

B703 (Scroll PLM)
[High][Low] form a pointer (bank $8F) to the scroll update data.*

*Format of scroll updating data is as follows:
(screen)(scroll)...(screen)(scroll)(80)
Example:
03 01 80 <--- change screen 03 to a blue scroll.

Super Metroid
List of PLMs